Reference:Polynomial
Poly, cubic and quartics are just like quadrics in that you do not have
to understand one to use one. The file shapesq.inc
has
plenty of pre-defined quartics for you to play with.
For convenience an alternate syntax is available as polynomial
. It doesn't care about the order of the coefficients, as long as you do not define them more than once, otherwise only the value of the last definition is kept. Additionally the default with all coefficients is 0, which can be especially useful typing shortcut.
See the tutorial section for more examples of the simplified syntax.
POLYNOMIAL: polynomial { Order, [COEFFICIENTS...] [POLY_MODIFIERS...] } COEFFICIENTS: xyz(<x_power>,<y_power>,<z_power>):<value>[,] POLY_MODIFIERS: sturm | OBJECT_MODIFIER
Same as the torus above, but with the polynomial syntax:
// Torus having major radius sqrt(40), minor radius sqrt(12) polynomial { 4, xyz(4,0,0):1, xyz(2,2,0):2, xyz(2,0,2):2, xyz(2,0,0):-104, xyz(0,4,0):1, xyz(0,2,2):2, xyz(0,2,0):56, xyz(0,0,4):1, xyz(0,0,2):-104, xyz(0,0,0):784 sturm }
The following table shows which polynomial terms correspond to which x,y,z
factors for the orders 2 to 7. Remember cubic
is actually a 3rd order polynomial and
quartic
is 4th order.
2^{nd} | 3^{rd} | 4^{th} | 5^{th} | 6^{th} | 7^{th} | 5^{th} | 6^{th} | 7^{th} | 6^{th} | 7^{th} | |||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A_{1} | x^{2} | x^{3} | x^{4} | x^{5} | x^{6} | x^{7} | A_{41} | y^{3} | xy^{3} | x^{2}y^{3} | A_{81} | z^{3} | xz^{3} |
A_{2} | xy | x^{2}y | x^{3}y | x^{4}y | x^{5}y | x^{6}y | A_{42} | y^{2}z^{3} | xy^{2}z^{3} | x^{2}y^{2}z^{3} | A_{82} | z^{2} | xz^{2} |
A_{3} | xz | x^{2}z | x^{3}z | x^{4}z | x^{5}z | x^{6}z | A_{43} | y^{2}z^{2} | xy^{2}z^{2} | x^{2}y^{2}z^{2} | A_{83} | z | xz |
A_{4} | x | x^{2} | x^{3} | x^{4} | x^{5} | x^{6} | A_{44} | y^{2}z | xy^{2}z | x^{2}y^{2}z | A_{84} | 1 | x |
A_{5} | y^{2} | xy^{2} | x^{2}y^{2} | x^{3}y^{2} | x^{4}y^{2} | x^{5}y^{2} | A_{45} | y^{2} | xy^{2} | x^{2}y^{2} | A_{85} | y^{7} | |
A_{6} | yz | xyz | x^{2}yz | x^{3}yz | x^{4}yz | x^{5}yz | A_{46} | yz^{4} | xyz^{4} | x^{2}yz^{4} | A_{86} | y^{6}z | |
A_{7} | y | xy | x^{2}y | x^{3}y | x^{4}y | x^{5}y | A_{47} | yz^{3} | xyz^{3} | x^{2}yz^{3} | A_{87} | y^{6} | |
A_{8} | z^{2} | xz^{2} | x^{2}z^{2} | x^{3}z^{2} | x^{4}z^{2} | x^{5}z^{2} | A_{48} | yz^{2} | xyz^{2} | x^{2}yz^{2} | A_{88} | y^{5}z^{2} | |
A_{9} | z | xz | x^{2}z | x^{3}z | x^{4}z | x^{5}z | A_{49} | yz | xyz | x^{2}yz | A_{89} | y^{5}z | |
A_{10} | 1 | x | x^{2} | x^{3} | x^{4} | x^{5} | A_{50} | y | xy | x^{2}y | A_{90} | y^{5} | |
A_{11} | y^{3} | xy^{3} | x^{2}y^{3} | x^{3}y^{3} | x^{4}y^{3} | A_{51} | z^{5} | xz^{5} | x^{2}z^{5} | A_{91} | y^{4}z^{3} | ||
A_{12} | y^{2}z | xy^{2}z | x^{2}y^{2}z | x^{3}y^{2}z | x^{4}y^{2}z | A_{52} | z^{4} | xz^{4} | x^{2}z^{4} | A_{92} | y^{4}z^{2} | ||
A_{13} | y^{2} | xy^{2} | x^{2}y^{2} | x^{3}y^{2} | x^{4}y^{2} | A_{53} | z^{3} | xz^{3} | x^{2}z^{3} | A_{93} | y^{4}z | ||
A_{14} | yz^{2} | xyz^{2} | x^{2}yz^{2} | x^{3}yz^{2} | x^{4}yz^{2} | A_{54} | z^{2} | xz^{2} | x^{2}z^{2} | A_{94} | y^{4} | ||
A_{15} | yz | xyz | x^{2}yz | x^{3}yz | x^{4}yz | A_{55} | z | xz | x^{2}z | A_{95} | y^{3}z^{4} | ||
A_{16} | y | xy | x^{2}y | x^{3}y | x^{4}y | A_{56} | 1 | x | x^{2} | A_{96} | y^{3}z^{3} | ||
A_{17} | z^{3} | xz^{3} | x^{2}z^{3} | x^{3}z^{3} | x^{4}z^{3} | A_{57} | y^{6} | xy^{6} | A_{97} | y^{3}z^{2} | |||
A_{18} | z^{2} | xz^{2} | x^{2}z^{2} | x^{3}z^{2} | x^{4}z^{2} | A_{58} | y^{5}z | xy^{5}z | A_{98} | y^{3}z | |||
A_{19} | z | xz | x^{2}z | x^{3}z | x^{4}z | A_{59} | y^{5} | xy^{5} | A_{99} | y^{3} | |||
A_{20} | 1 | x | x^{2} | x^{3} | x^{4} | A_{60} | y^{4}z^{2} | xy^{4}z^{2} | A_{100} | y^{2}z^{5} | |||
A_{21} | y^{4} | xy^{4} | x^{2}y^{4} | x^{3}y^{4} | A_{61} | y^{4}z | xy^{4}z | A_{101} | y^{2}z^{4} | ||||
A_{22} | y^{3}z | xy^{3}z | x^{2}y^{3}z | x^{3}y^{3}z | A_{62} | y^{4} | xy^{4} | A_{102} | y^{2}z^{3} | ||||
A_{23} | y^{3} | xy^{3} | x^{2}y^{3} | x^{3}y^{3} | A_{63} | y^{3}z^{3} | xy^{3}z^{3} | A_{103} | y^{2}z^{2} | ||||
A_{24} | y^{2}z^{2} | xy^{2}z^{2} | x^{2}y^{2}z^{2} | x^{3}y^{2}z^{2} | A_{64} | y^{3}z^{2} | xy^{3}z^{2} | A_{104} | y^{2}z | ||||
A_{25} | y^{2}z | xy^{2}z | x^{2}y^{2}z | x^{3}y^{2}z | A_{65} | y^{3}z | xy^{3}z | A_{105} | y^{2} | ||||
A_{26} | y^{2} | xy^{2} | x^{2}y^{2} | x^{3}y^{2} | A_{66} | y^{3} | xy^{3} | A_{106} | yz^{6} | ||||
A_{27} | yz^{3} | xyz^{3} | x^{2}yz^{3} | x^{3}yz^{3} | A_{67} | y^{2}z^{4} | xy^{2}z^{4} | A_{107} | yz^{5} | ||||
A_{28} | yz^{2} | xyz^{2} | x^{2}yz^{2} | x^{3}yz^{2} | A_{68} | y^{2}z^{3} | xy^{2}z^{3} | A_{108} | yz^{4} | ||||
A_{29} | yz | xyz | x^{2}yz | x^{3}yz | A_{69} | y^{2}z^{2} | xy^{2}z^{2} | A_{109} | yz^{3} | ||||
A_{30} | y | xy | x^{2}y | x^{3}y | A_{70} | y^{2}z | xy^{2}z | A_{110} | yz^{2} | ||||
A_{31} | z^{4} | xz^{4} | x^{2}z^{4} | x^{3}z^{4} | A_{71} | y^{2} | xy^{2} | A_{111} | yz | ||||
A_{32} | z^{3} | xz^{3} | x^{2}z^{3} | x^{3}z^{3} | A_{72} | yz^{5} | xyz^{5} | A_{112} | y | ||||
A_{33} | z^{2} | xz^{2} | x^{2}z^{2} | x^{3}z^{2} | A_{73} | yz^{4} | xyz^{4} | A_{113} | z^{7} | ||||
A_{34} | z | xz | x^{2}z | x^{3}z | A_{74} | yz^{3} | xyz^{3} | A_{114} | z^{6} | ||||
A_{35} | 1 | x | x^{2} | x^{3} | A_{75} | yz^{2} | xyz^{2} | A_{115} | z^{5} | ||||
A_{36} | y^{5} | xy^{5} | x^{2}y^{5} | A_{76} | yz | xyz | A_{116} | z^{4} | |||||
A_{37} | y^{4}z | xy^{4}z | x^{2}y^{4}z | A_{77} | y | xy | A_{117} | z^{3} | |||||
A_{38} | y^{4} | xy^{4} | x^{2}y^{4} | A_{78} | z^{6} | xz^{6} | A_{118} | z^{2} | |||||
A_{39} | y^{3}z^{2} | xy^{3}z^{2} | x^{2}y^{3}z^{2} | A_{79} | z^{5} | xz^{5} | A_{119} | z | |||||
A_{40} | y^{3}z | xy^{3}z | x^{2}y^{3}z | A_{80} | z^{4} | xz^{4} | A_{120} | 1 |
Polynomial shapes can be used to describe a large class of shapes
including the torus, the lemniscate, etc. For example, to declare a quartic
surface requires that each of the coefficients (A1 ...
A35
) be placed in order into a single long vector of 35 terms. As an example let's define a torus the hard way. A Torus can be represented by the equation: x^{4} + y^{4} + z^{4} + 2 x^{2} y^{2} + 2 x^{2} z^{2} + 2 y^{2} z^{2} - 2 (r_02 + r_12)
x^{2} + 2 (r_02 - r_12) y^{2} - 2 (r_02 + r_12) z^{2} + (r_02 - r_12)^{2} = 0
Where r_0 is the major radius of the torus, the distance from the hole of the donut to the middle of the ring of the donut, and r_1 is the minor radius of the torus, the distance from the middle of the ring of the donut to the outer surface. The following object declaration is for a torus having major radius 6.3 minor radius 3.5 (Making the maximum width just under 20).
// Torus having major radius sqrt(40), minor radius sqrt(12) quartic { < 1, 0, 0, 0, 2, 0, 0, 2, 0, -104, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 56, 0, 0, 0, 0, 1, 0, -104, 0, 784 > sturm }
Polynomial surfaces use highly complex computations and will not always render perfectly.
If the surface is not smooth, has dropouts, or extra random pixels, try using
the optional keyword sturm
in the definition. This will cause a
slower but more accurate calculation method to be used. Usually, but not
always, this will solve the problem. If sturm does not work, try rotating
or translating the shape by some small amount.
There are really so many different polynomial shapes, we cannot even begin to list or describe them all. We suggest you find a good reference or text book if you want to investigate the subject further.